FIG. 6 shows the conventional constitution of an audio-visual system (AV system). In this AV system, a source device 50 such as a DVD player is connected to an AV amplifier 60 via an HDMI cable 71. The AV amplifier 60 is connected to a television receiver (TV) 80 via an HDMI cable 72. The AV amplifier 60 is connected to speakers 90 via an analog audio output cable 73.
When a source device (i.e. a transmitter device) is connected to a sink device (i.e. a receiver device) such as the AV amplifier 60 and the TV 80, these devices mutually exchange their device information, including reproduction ability information of the sink device, called EDID (Extended Display Identification Data) therebetween upon establishment of a connection, so that an authentification is implemented between the source device and the sink device. When the source device 50 transmits audio data to sink devices, transmission of audio data is carried out in connection with a sink device with the lowest audio reproduction ability. In the conventional AV system shown in FIG. 6, the source device 50 transmits audio data to the AV amplifier 60 in accordance with an audio reproduction ability of the TV 80 having a smaller number of audio channels among two sink devices (i.e. the AV amplifier 60 and the TV 80). When the TV 80 has a 2ch audio reproduction ability irrespective of a 5.1ch audio reproduction ability of the AV amplifier 60, the source device 50 carries out down-mixing on audio data, given by a 5.1 ch audio source, so as to transmit 2ch-compatible audio data to the AV amplifier 60.
Patent Document 1 provides a solution to this problem with reference to the AV system shown in FIG. 6, wherein EDID representing an audio reproduction ability of the AV amplifier 60 is sent to the source device 50 when the TV 80 does not provide an audio output, whilst EDID representing an audio reproduction ability of the TV 80 is sent to the source device 50 when the TV 80 provides an audio output. Thus, the AV amplifier 60 and the TV 80 are able to receive audio data from the source device 50 in response to the numbers of audio channels.